Ultrasonic sealing device for packaging material

ABSTRACT

A belt-like film  18  is moved along a plate  15  folded to be rectangular in section, so that the film  18  is formed into a continuous tube by a tubular frame of the plate  15 . A spring piece  30  having an anvil  31  bulged out therefrom is securely held on the inner side edge  16  of the aforementioned plate  15 , and an ultrasonic hammer  32  is located face to face with said anvil  31 , so that both side edges of the belt-like film  18  formed into a tube are placed on the anvil  31  to be melded by the ultrasonic vibration of the hammer  32.

TECHNICAL FIELD

The present invention relates to a device not only for rounding abelt-like film into a tube along its length direction, but for meldingoverlapped edges on both sides of said tubular film by ultrasonicvibration in order to form a plurality of packaging bags.

BACKGROUND ART

In the conventional device which effects melding of overlapped parts ofboth side edges of a film rounded to be tubular by heat generated byultrasonic vibration, as shown in FIG. 7, two overlapping sheets of film13 are moved in the direction of arrow 14 between a vertically vibratinghammer 10 and an anvil 12 securely held on the frame 11, thereby tocontinuously meld the film 13 by vibration heat induced by the hammer.However, because of subtle variations in the thickness of theaforementioned film 13, its melding strength varies from area to area,threatening to cause air leak when vacuum packaging is carried out, forexample.

DISCLOSURE OF INVENTION

It is therefore an object of this invention to form a tubular filmhaving a uniform strength by averaging the vibratory impact force to beapplied onto the film.

The present invention provides a sealing device comprising a means formoving a belt-like film along a tubular plate having both side edgesthereof folded to overlap one upon another as if at a kimono's neckpart, thereby to form the film into a continuous tube, following thesectional profile of this tubular plate, wherein an anvil is formed onone end of a spring piece, the other end of which is fixedly set on oneside edge of the aforementioned overlapped part of the tubular plate,the overlapped portion of the tubular film may be melded by thecooperation of the aforementioned anvil and a movable hammer whichapplies an ultrasonic vibratory impact on said anvil.

Further, the present invention provides a sealing device comprising ameans for moving a belt-like film along the inner surface of a tubularplate so folded as to form a continuous slit between both side edgesthereof, thereby to form said film into a continuous tube, following thesectional profile of this tubular plate, wherein one end of a springpiece is fixedly set to a base block immovably held on one of the sidessandwiching the aforementioned slit, and an anvil is formed on the otherend of said spring piece, so that clasped-hands like edges of thetubular film which are thrusted out from the aforementioned anvil may bemelded by the cooperation of the aforementioned anvil and a movablehammer which applies ultrasonic vibratory impact on said anvil.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a bottom view of a sealing device according to an embodimentof the invention;

FIG. 2 is a perspective view of the device;

FIG. 3 is a sectional view of the device along the line III—III in FIG.2;

FIG. 4 is a sectional view of the device taken along the line IV—IV inFIG. 2;

FIG. 5 is a side view of a sealing device according to a secondembodiment of the invention;

FIG. 6 is a sectional view of the device taken along the line IV—IV inFIG. 5;

FIG. 7 is an explanatory diagram showing a prior art.

BEST MODE FOR CARRYING OUT THE INTENTION

As shown in FIG. 1 and FIG. 2 which is a perspective view of FIG. 1, aplate 15 tubularly folded to be rectangular in section is not onlyoverlapped at two side edges 16 and 17 thereof with one upon the otheras if at a kimono's neck part, but has inclined edges 20 and a V-shapeedge 21 provided at the entrance 19 for a belt-like film 18 in order toreduce resistance accompanying said film's access thereto. With thisarrangement, one side edge 22 of the film 18 which is drawn out alongsaid tubular plate 15 passes under the inner side edge 16, and the otherside edge 23 passes under the outer edge 17. However, in this instance,as a part of the inner edge 16 is stealthily notched as at 24, the oneside edge 22 of the film is led out upward through this stealthilynotched part 24. As a result, two side edges 22A and 23A are overlappedas if at a kimono's neck part at a position where they come out from theaforementioned stealthily notched part (see also FIG. 4).

Further, one end of an elongated rectangular spring piece 30 is securelyheld on the inner surface of the central portion of the inner side edge16 of the aforementioned tubular plate, while a grain-of-rice shapeanvil 31 is bulged out from the other free end of said spring piece andan ultrasonic hammer 32 is located face to face with said anvil 31, asshown in FIG. 4. When ultrasonic vibration of the aforementioned hammer32 is acted upon the anvil 31 through the film, the film melds to form atubular shape due to heat produced by this vibration. In this instance,the aforementioned spring piece 30 is flexible, so that even if the film18's thickness is more or less uneven, vibratory impact is uniformlyapplied on the film owing to the flexibility of the spring piece,thereby equalizing the meld strength.

According to the description of the embodiment represented by FIGS. 1through 4, the belt-like film 18 is formed into a tube by drawing itdownward from the tubular plate 15, however it is also possible to turnround a tubular film for 180 degrees and lead the film downward fromabove. This attests to its inverse operability, as in the followingembodiment.

As shown in FIGS. 5 and 6, a tubular plate 41 affixed to a frame 40 hasa contiguous slit 42 formed along the center line of the bottom thereof.A belt-like film 43 is led down from above, and its two side edges 44are rounded, while being thrusted out in the form of clasped handsthrough the aforementioned slit 42.

On the bottom surface of the aforementioned tubular plate, there is hunga base block 45 from one of the sides sandwiching the aforementionedslit 42. Said base block is affixed with an elongated rectangular springpiece 46 affixed at one end thereof, and an anvil 47 is bulged out fromsaid spring piece at the other end thereof. On the other hand, a hammer50 of a bell crank 49 supported on the frame 48 is placed face to facewith the aforementioned anvil 47, and the aforementioned bell crank iscoupled to a vibrator 51. When vibration is acted on the anvil throughthe hammer 50 by the power from the aforementioned vibrator 51, theclasped-hands shape portion of the film thrusted out through the slit 42is moved while being continuously melded.

It should be noted that the objective may alternatively be achieved bysecuring the aforementioned base block 45 on the frame in an immovablestate instead of on the tubular plate 41. Further, the respective springpieces in both embodiments shown in FIGS. 1 and 6 may be made by usingother materials than those specified exclusively for springs, as far asthe used material has such an elasticity that the spring pieces wouldnot be deformed by the vibration amplitude of the hammer, because theamplitude is very small.

What is claimed is:
 1. A sealing device comprising: a tubular platehaving two side edges thereof folded to overlap one upon another as ifat a kimono's neck part; a means for moving a belt-like film along thetubular plate following a sectional profile of the tubular plate to formthe film into a continuous tube; a spring piece with one end fixedly seton one side edge of the aforementioned overlapped part of the tubularplate, and an anvil formed on the other end of the spring piece formelding an overlapped portion of the tubular film in cooperation with amovable hammer which applies ultrasonic vibratory impact on the anvil.2. A sealing device comprising: a tubular plate so folded as to form acontinuous slit between two side edges thereof; a means for moving abelt-like film along an inner surface of the tubular plate following asectional profile of the tubular plate to form the film into acontinuous tube; a spring piece with one end fixedly set to a base blockimmovably held on one of the sides of the tubular plate sandwiching theaforementioned slit; and an anvil formed on the other end of the springpiece for melding clasped-hands like edges of the tubular film which arethrusted out from the aforementioned slit in cooperation with a movablehammer which applied ultrasonic vibratory impact on said anvil.